Unified Objective Lens for Imaging and Scatterometry

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current metrology tools require two separate optical heads for imaging and scatterometry overlay metrology due to differing optical specifications, leading to increased size and complexity, as well as higher production and maintenance costs.

Innovation Solution

Designing an objective lens with a central region conforming to specified imaging requirements and a peripheral region conforming to scatterometry requirements, using common-path optical elements to handle both imaging and scatterometry signals, thereby simplifying the optical system and eliminating the need for two separate heads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If two separate optical heads are used for imaging and scatterometry metrology, then the performance requirements for both imaging and scatterometry are met, but the device size and complexity increase

Engineering Contradiction:

Improveperformance requirement fulfillmentVSAvoidoptical system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines two separate optical heads (imaging and scatterometry) into a single unified optical head. The objective lens is designed with a central region optimized for imaging and a peripheral region optimized for scatterometry, allowing both metrology functions to be performed through one integrated system rather than requiring two separate systems.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The unified objective lens serves multiple functions by having different regions optimized for different metrology techniques. The central region handles imaging overlay metrology while the peripheral region handles scatterometry overlay metrology, making the single optical head universal for both purposes.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If two separate optical heads are used for imaging and scatterometry metrology, then the performance requirements for both imaging and scatterometry are met, but production and maintenance costs increase

Engineering Contradiction:

Improveperformance requirement fulfillmentVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #5Merging (Combining)

3Device complexity

If a single objective lens is used for both imaging and scatterometry, then the device size and complexity are reduced, but it is difficult to meet differing optical specifications for both functions

Engineering Contradiction:

Improveoptical system complexityVSAvoidoptical specification compliance

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The objective lens is designed with non-uniform optical properties across its aperture. The central region has optical characteristics optimized for imaging metrology, while the peripheral region has optical characteristics optimized for scatterometry metrology. This spatial variation in optical quality allows each region to meet its specific functional requirements within a single lens.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The objective lens aperture is effectively segmented into functional zones: a central region for imaging and a peripheral region for scatterometry. Each segment is optimized for its specific function, allowing the single lens to satisfy the different optical specifications required by the two metrology techniques.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS10139528B1Compound objectives for imaging and scatterometry overlay

Publication Date: 2018.11.27 KLA CORP

AI summary

Objective lenses and corresponding optical systems and metrology tools, as well as methods are provided. Objective lenses comprise a central region conforming to specified imaging requirements and a peripheral region conforming to specified scatterometry requirements. The optical systems may comprise common-path optical elements configured to handle both imaging and scatterometry signals received through the objective lens. Using a single objective lens simplifies the design of the optical system while maintaining, simultaneously, the performance requirements for imaging as well as for scatterometry.